Was there a formal edict or law which mandated that Vlachs had to "receive new names" from the state?

It wasn't just the "Vlachs" who received new (sur)names. The "literary" Macedonian -ski ending was the system adopted in the Macedonian Republic from 1944, and it impacted many Macedonians as well.

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True. The Vlachs (those who weren't suckered in by the Greeks) were probably the only ethnic group that provided a notable level of support to the Macedonians in their quest for a free Macedonia. Those who sacrificed their lives for the cause deserve nothing less than respect. Macedonia honours its Vlach heroes. Too bad many of their descendants aren't as passionate about the idea of a sovereign Macedonia today.

There is some truth to that, but nearly all of the minorities claim their numbers were/are much higher and/or have decreased due to assimilation. If we were to take them all at face value, then actual Macedonians have been an ethnic minority in their own fatherland for quite some time. Meanwhile, most records from the 19th century clearly indicate that the cultural and linguistic ancestors of today's ethnic Macedonians were the majority in the territory of the Macedonian republic. Go figure.

I'm not sure what the "exact" number of Vlachs is in Macedonia. As I said, I actually believe that Vlachs as a separate community hardly exist nowadays due to widespread intermarriage and primarily identify as Macedonians. As a result of the intermarriage, most "Vlachs" nowadays are mixed, and vice versa. There are a lot of Macedonians who have at least a Vlach grandfather or Vlach grandmother in their family line, i.e. the late Ljubisha Georgievski, who was basically half-Vlach as he himself explains here (minute 2:05 to 3:05):https://www.youtube.com/watch?v=0bau6PFnGzc